We're going to begin with the growing mystery of what happened to 10-year-old jessica ridgeway of colorado, who vanished on her way to school. What began as a search for this little girl is now a desperate hunt for her killer. Abc's clayton sandell tells us how the fbi is hoping to break this case open. Reporter: Officers are searching fields, ravines and neighborhoods near where a body was discovered late wednesday. Sources tell abc news, the remains belong to 10-year-old jessica ridgeway, who vanished a week ago, walking to school in nearby westminster. But a frustrating lack of suspects is now prompting investigators to release a profile of who they believe committed this gruesome crime. That would be your boss, your friend, and ultimately could be your family member. Reporter: The new profile by the behavioral analysis unit says the likely suspect is probably male. And may have missed work or suddenly left town. He may have already changed his appearance. Or gotten rid of his car. Abc news has learned investigators are focusing on cell phone towers near jessica's home, where her backpack was found, and where the remains were discovered. If a phone number registered at all three towers, it could led to a suspect. We all have children of her own. And it could have been our child. Reporter: And this morning, the entire community remains on-edge. For "good morning america," clayton sandell, westminster, colorado.

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